Fluid handling valves, e.g., fluid dispense valves, are used in applications where the valve internals are subjected to corrosive acidic or caustic liquids, or where the purity of the liquids which flow through the valve must be maintained. An example of such application is the semiconductor manufacturing industry where the process chemical delivered through such a valve must maintain a high degree of chemical purity to avoid contamination that may occur on the microscopic level, and that is know to cause damage to the manufactured product, e.g., a semiconductor wafer.
It is also desired, during certain process steps, that a precise amount of the process chemical be deposited onto the product. It is, therefore, important that a dispense valve used to perform such function be capable of repeatably dispensing an accurate volume of the process liquid without dribbling excess liquid onto the product after the valve has been shut. It is, however, known in the industry that dispense valves used to perform this function do not always terminate the dispensement of liquid after the valve is closed or shut.
For example, conventional dispense valves used in this capacity are known to cavitate and/or seep out a small volume of liquid after the valve has been closed. This extra volume of liquid is either dispensed from the valve onto the product, providing an undesired excess of the delivered liquid, or is retained within the outlet port of the valve or the ultimate delivery device, e.g., a pipe or nozzle. In the case where the excess liquid is retained within the valve, this situation too presents a problem because the liquid can dry near the tip of the ultimate delivery device. The dried portion of liquid can then be dispensed onto a product the next time that a volume of the process liquid is delivered from the dispensing valve. Delivery of such dried portion of the liquid onto the product is known to cause damage to the product and, thus, is not desired.
It is, therefore, desired that a dispense valve be designed in such a manner so as to control and/or eliminate the potential for liquid cavitation and/or excess liquid seepage and/or delivery once the valve has been shut or closed. It is also desired that such a dispense valve be configured to enable its operation with chemically aggressive and/or pure liquids without degrading or otherwise functioning in a manner that could introduce contaminate material into the liquid. It is further desired that such dispense valve be constructed in a manner so as to reduce the number of liquid leak paths therethrough, thereby reducing the possibility of chemical leakage to the outside environment.